U.S. patent application number 13/324616 was filed with the patent office on 2012-07-19 for bone anchoring device.
Invention is credited to Lutz BIEDERMANN, Tobias Hagle, Wilfried Matthis.
Application Number | 20120185003 13/324616 |
Document ID | / |
Family ID | 43778643 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120185003 |
Kind Code |
A1 |
BIEDERMANN; Lutz ; et
al. |
July 19, 2012 |
BONE ANCHORING DEVICE
Abstract
A bone anchoring device includes a bone anchoring element having
a head and a shaft, a receiving part for coupling the bone
anchoring element to a stabilization element, the receiving part
having a bore having a bore axis, a seat member configured to be
arranged in the bore and to be rotatable around the bore axis, the
seat member forming a seat for polyaxially holding the head, the
seat member being configured to allow a greater pivot angle of the
bone anchoring element in a first direction compared to other
directions when the bone anchoring element and the seat member are
in the receiving part, and a pressure member configured to contact
the head to exert pressure onto the head, and to be connected to
the seat member, such that the pressure member is rotatable
together with the seat member around the bore axis.
Inventors: |
BIEDERMANN; Lutz;
(VS-Villingen, DE) ; Matthis; Wilfried; (Weisweil,
DE) ; Hagle; Tobias; (Donaueschingen, DE) |
Family ID: |
43778643 |
Appl. No.: |
13/324616 |
Filed: |
December 13, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61422538 |
Dec 13, 2010 |
|
|
|
Current U.S.
Class: |
606/328 ;
29/428 |
Current CPC
Class: |
A61B 17/7037 20130101;
A61B 17/7038 20130101; Y10T 29/49826 20150115; A61B 17/7035
20130101; A61B 17/7032 20130101; A61B 17/8605 20130101 |
Class at
Publication: |
606/328 ;
29/428 |
International
Class: |
A61B 17/84 20060101
A61B017/84; B23P 11/00 20060101 B23P011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2010 |
EP |
EP 10 194 787.7 |
Claims
1. A bone anchoring device comprising: a bone anchoring element
having a head and a shaft configured to be anchored in a bone or a
vertebra; a receiving part for coupling the bone anchoring element
to a stabilization element, the receiving part having a first end,
a second end, a bore extending from the first end to the second end
and having a bore axis, and a recess for receiving a stabilization
element, the recess being in communication with the bore; a seat
member configured to be arranged in the bore and to be rotatable
around the bore axis, the seat member forming a seat for
polyaxially holding the head, the seat member being configured to
allow a greater pivot angle of the bone anchoring element in a
first direction relative to the bore axis compared to other
directions relative to the bore axis when the bone anchoring
element and the seat member are in the receiving part; and a
pressure member configured to contact the head to exert pressure
onto the head, and to be connected to the seat member, such that
the pressure member is rotatable together with the seat member
around the bore axis, so as to allow for adjustment of an
orientation of the first direction relative to the bore axis when
the bone anchoring element, the seat member, and the pressure
member are in the receiving part.
2. The bone anchoring device of claim 1, wherein when the bone
anchoring element, the seat member, and the pressure member are in
the receiving part, the pressure member is axially movable with
respect to the seat member.
3. The bone anchoring device of claim 1, wherein the pressure
member is connectable to the seat member so as to transmit
rotational forces to the seat member.
4. The bone anchoring device of claim 1, wherein when the seat
member is in the receiving part, the seat member abuts against a
stop in the receiving part.
5. The bone anchoring device of claim 1, wherein the seat member
has at east a partially spherical inner surface.
6. The bone anchoring device of claim 1, wherein when the seat
member is in the receiving part, the seat member projects at least
partly out of the second end of the receiving part in a direction
away from the first end of the receiving part.
7. The bone anchoring device of claim 1, wherein the seat member
has an inclined lower edge to provide the greater pivot angle in
the first direction for an inserted bone anchoring element.
8. The hone anchoring device of claim 1, wherein the pressure
member and the seat member are connectable via a form lock
connection.
9. The bone anchoring device of claim 8, wherein the seat member
has at least one recess or projection for engaging a corresponding
projection or recess at the pressure member.
10. The bone anchoring device of claim 1, wherein the pressure
member has an engagement portion for engagement with a driver or
tool.
11. The bone anchoring device of claim 10, wherein the engagement
portion is provided at a side of the pressure member which faces
away from the head when the bone anchoring element, the seat
member, and the pressure member are in the receiving part.
12. The bone anchoring device of claim 1, wherein the seat member
and the pressure member each comprises a cylindrical portion,
wherein when the respective cylindrical portions are engaged, the
cylindrical portions are configured to be axially movable but
rotationally fixed relative to one another.
13. The bone anchoring device of claim 1, wherein the pressure
member is a first pressure member, and wherein the bone anchoring
device further comprises a second pressure member configured to be
positioned in the receiving part on a side of the first pressure
member opposite the head, and wherein the second pressure member
has a recess for guiding a stabilization element.
14. The bone anchoring device of claim 13, wherein the second
pressure member is configured to press onto the first pressure
member without touching the seat member to lock the head in the
seat member.
15. The bone anchoring device of claim 13, wherein the second
pressure member is rotatable with respect to the first pressure
member when the first pressure member and the second pressure
member are engaged in the receiving part.
16. The bone anchoring device of claim 13, wherein the second
pressure member is securable against rotation in the receiving
part.
17. The bone anchoring device of claim 1, wherein the recess for
receiving a stabilization element is U-shaped.
18. A method for adjusting a pivot angle of a polyaxial bone
anchoring device, the bone anchoring device comprising a bone
anchoring element having a head and a shaft configured to be
anchored in a bone or a vertebra, a receiving part for coupling the
bone anchoring element to a stabilization element, the receiving
part having a first end, a second end, a bore extending from the
first end to the second end and having a bore axis, and a
substantially U-shaped recess for receiving a stabilization
element, the recess being in communication with the bore, and a
seat member arranged in the bore and rotatable around the bore
axis, the seat member forming a seat for polyaxially holding the
head, the seat member being configured to allow a greater pivot
angle of the bone anchoring element in a first direction relative
to the bore axis compared to other directions relative to the bore
axis, the method comprising: supporting at least one of the seat
member or the receiving part in and fixed relative to a support
device; and rotating the receiving part with respect o the seat
member to adjust an orientation of the first direction relative to
the bore axis.
19. The method of claim 18, wherein the seat member is supported in
a recess in the support device in a form locking manner.
20. A method of coupling a stabilization element to a bone via a
polyaxial bone anchoring device, the bone anchoring device
comprising a bone anchoring element having a head and a shaft
configured to be anchored in a bone, a receiving part for coupling
the bone anchoring element to a stabilization element, the
receiving part having a first end, a second end, a bore extending
from the first end to the second end and having a bore axis, and a
recess for receiving a stabilization element, the recess being in
communication with the bore, a seat member configured to be
arranged in the bore and to be rotatable around the bore axis, the
seat member forming a seat for polyaxially holding the head, the
seat member being configured to allow a greater pivot angle of the
bone anchoring element in a first direction relative to the bore
axis compared to other directions relative to the bore axis when
the bone anchoring element and the seat member are in the receiving
part, and a pressure member configured to contact the head to exert
pressure onto the head and to be connected to the seat member, such
that the pressure member is rotatable together with the seat member
around the bore axis, the method comprising: inserting the bone
anchoring device into a bone, the bone anchoring device comprising
the receiving part with at least the bone anchoring element and the
seat member inserted therein; connecting the pressure member to the
seat member; rotating the pressure member to rotate the seat member
and to adjust an orientation of the first direction relative to the
bore axis; tilting the receiving part relative to the bone
anchoring element substantially along the first direction;
inserting a stabilization element into the recess; and advancing a
closure element into the recess to push the stabilization element
and the pressure member towards the second end of the receiving
part, wherein the pressure element is pushed against the head to
lock positions of the seat member and the bone anchoring element
relative to the receiving part.
21. The method of claim 20, wherein prior to inserting the bone
anchoring device into the bone, the method further comprises:
inserting the seat member into the receiving part; and inserting
the head of the bone anchoring element into the seat member.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] The present application claims the benefit of U.S.
Provisional Patent Application Ser. No. 61/442,538, filed Dec. 13,
2010, the contents of which are hereby incorporated by reference in
their entirety, and claims priority to European Patent Application
EP 10 194 787.7, filed Dec. 13, 2010, the contents of which are
hereby incorporated by reference in their entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The invention relates to a bone anchoring device which
includes a bone anchoring element for anchoring in a bone or a
vertebra and a receiving part for coupling the bone anchoring
element to a stabilization element such as a spinal rod, where the
bone anchoring element is pivotable in the receiving part and can
be pivoted to at least one side with an enlarged pivot angle.
[0004] 2. Description of Related Art
[0005] A bone anchoring device of this type is described in U.S.
Pat. No. 6,736,820. The bone anchoring device includes a bone screw
and a receiving part with an open first bore and a substantially
U-shaped cross-section for receiving the rod and a second bore on
the end opposite to the first bore and a seat for the head. In
order that the screw member can be pivoted to at least one side by
an enlarged angle, the edge bounding the free end of the second
bore is of asymmetric construction. In a modified embodiment an
insert piece is provided, which has a spherical bottom as the seat
for the head. This allows to change the orientation of the enlarged
pivot angle.
[0006] US 2005/0154391 A1 describes a bone anchor assembly with a
bone anchor and a receiving member. The receiving member has a
first section having a first bore defining a first bore axis and a
second section having a second bore defining a second bore axis and
being sized to receive at least a portion of the bone anchor,
wherein the second bore axis intersects the first bore axis. The
second section is rotatable about the first bore axis. In an
embodiment, the second section is seated internally within the
first section.
[0007] Since the second section is rotatable with respect to the
first section, it is possible to pivot bone anchors out of
alignment with one another to avoid interference due to the close
proximity of adjacent vertebrae.
[0008] Another polyaxial bone anchor is described in US
2007/0118123 A1, wherein a locking element is provided, which is
shaped and configured to allow an anchoring member such as a screw
or a hook to polyaxially rotate at large angles about a central
axis of the bone anchor before compression locking the anchoring
member within an anchor head.
SUMMARY
[0009] With the bone anchoring devices mentioned above, it may be
difficult to adjust a position in which a bone anchoring element
has an enlarged pivot angle once the bone anchoring element is
partly or fully inserted into a bone.
[0010] It is an object of embodiments of the invention to provide
an improved bone anchoring device that facilitates adjustment of a
direction of an enlarged pivot angle of the bone anchoring
element.
[0011] A bone anchoring device according to an embodiment of the
invention allows rotation of a seat member that holds a head of a
bone anchoring element by means of, for example, a driver or tool
inserted from a top end of the receiving part, so that a direction
of pivoting can be adjusted to any desired direction. The
orientation of the driver, for example, the orientation of a handle
of the driver, can be used as a precise indicator of the
orientation of the seat member. Hence, it is possible or easier to
adjust the direction of an enlarged pivot angle during surgery.
[0012] Some embodiments may provide a way to pre-adjust the
orientation of the seat member using a single support block that
fixes the seat member, and then rotating the receiving part
relative to the seat member.
[0013] The locking of the head in the seat member is effected by
pressure exerted from above onto the head, which is then pressed
against the seat. Therefore, the locking of the head can be
effected in a safe and predictable manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Further features and advantages of the invention will become
apparent from the description of embodiments by means of the
accompanying drawings. In the drawings:
[0015] FIG. 1 shows a perspective exploded view of a bone anchoring
device with a spinal rod according to an embodiment of the
invention;
[0016] FIG. 2 shows the bone anchoring device of FIG. 1 in an
assembled state without a rod or a fixation screw;
[0017] FIG. 3 shows a cross-sectional view of the bone anchoring
device of FIG. 1, the section being taken perpendicular to a rod
axis;
[0018] FIG. 4 shows a cross-sectional view of the bone anchoring
device of FIG. 1, the section being taken along the rod axis;
[0019] FIG. 5 shows a perspective view of a seat member of the bone
anchoring device according to an embodiment of the invention;
[0020] FIG. 6 shows a side view of the seat member of FIG. 5;
[0021] FIG. 7 shows a cross-sectional view of the seat member of
FIGS. 5 and 6, the section being taken along line A-A in FIG.
6;
[0022] FIG. 8 shows a perspective view of a first pressure member
of the bone anchoring device according to an embodiment of the
invention;
[0023] FIG. 9 shows a top view of the first pressure member of FIG.
8;
[0024] FIG. 10 shows a side view of the first pressure member of
FIG. 8;
[0025] FIG. 11 shows a cross-sectional view of the first pressure
member of FIGS. 8-10 along line B-B of FIG. 10;
[0026] FIG. 12 shows a perspective view of a second pressure member
of the bone anchoring device from below, according to an embodiment
of the invention;
[0027] FIG. 13 shows a top view of the second pressure member of
FIG. 12;
[0028] FIG. 14 shows a cross-sectional view of the second pressure
member of FIGS. 12 and 13 along line C-C of FIG. 13;
[0029] FIG. 15 shows a cross-sectional view of a bone anchoring
element, a seat member and a first pressure member according to an
embodiment of the invention;
[0030] FIG. 16 shows a perspective view of an assembly including
the bone anchoring element, the seat member and the first pressure
member as seen in FIG. 15;
[0031] FIGS. 17a to 17c show steps of use of the bone anchoring
device according to the first embodiment;
[0032] FIGS. 18a to 18c show steps of adjusting the seat member
relative to the receiving part according to a first exemplary
embodiment;
[0033] FIG. 19 shows a top view of a support block for adjusting
the seat member relative to the receiving part as shown in FIGS.
18a-18c;
[0034] FIG. 20 shows a cross-sectional view of the support block of
FIGS. 18a-18c, with a bone anchoring device inserted, the section
being taken along a rod axis;
[0035] FIG. 21 shows a perspective view of a bone anchoring device
with an insertion tool according to an embodiment of the
invention;
[0036] FIG. 22 shows an enlarged portion of the device of FIG. 21;
and
[0037] FIG. 23 shows a perspective view of a bone anchoring device
and a portion of another embodiment of an insertion tool.
DETAILED DESCRIPTION
[0038] As shown in FIGS. 1 and 2, a bone anchoring device according
to an embodiment of the invention includes a bone anchoring element
1 in the form of a bone screw having a threaded shaft 2 and a head
3. The head 3 is typically spherically-shaped and has a recess 3a
for engagement with a driver or tool. The head 3 can be held in a
receiving part 4 that couples the bone anchoring element 1 to a
stabilization rod 100. In the receiving part 4, a seat member 5 for
providing a seat for the head 3, a first pressure member 6, and a
second pressure member 7 for exerting pressure onto the head 3 may
be arranged. Further, a fixation element in the form of, for
example, a fixation screw 8 is provided for securing and fixing the
rod 100 in the receiving part 4. When the bone anchoring device is
assembled but an angular position of the bone anchoring element 1
relative to receiving part 4 is not yet fixed, the bone anchoring
element 1 can pivot with an enlarged pivot angle in an unlimited
number of directions, as shown by the arrows in FIG. 2, depending
on a position of the seat member 5 within the receiving part 4.
[0039] The receiving part 4 will be described with reference to
FIGS. 1 to 4. The receiving part 4 has a top end 4a and a bottom
end 4b, a central axis C, and a coaxial bore 9 extending from the
top end 4a to the bottom end 4b. Adjacent to the top end 4a, a
substantially U-shaped recess 10 is provided, which forms a channel
for receiving the rod 100. By means of the recess 10, two free legs
11a, 11b are formed, which may be provided with an internal thread
12 for cooperating with the fixation screw 8. At the lower portion
of the bore 9 near the bottom end 4b, a stop 13 in the form of an
annular edge is provided for preventing the seat member 5 from
escaping through an opening 14 at the bottom end 4b. It shall be
noted that the bore 9 is not restricted to the specific shape of
the bore shown in the drawings, but can, for example, have
different portions with different diameters.
[0040] The seat member 5 is shown in particular in FIGS. 5 to 7.
The seat member 5 has a hollow cylindrical first portion 15, an
inner diameter of which is slightly larger than a maximum diameter
of the spherically-shaped head 3, and an outer diameter of which is
slightly smaller than an inner diameter of the bore 9, so that the
seat member 5 is insertable into the bore 9. An axial length of the
first portion 15 is such that when the head 3 rests within a seat
portion 16, the first portion 15 may project above the head 3.
Adjacent the first portion 15, the seat member 5 has a hollow
second portion 16, which has an internal spherically-shaped surface
16a for providing a seat for the spherically-shaped head 3. An
outer surface 16b of the second portion 16 is also
spherically-shaped, with an outer diameter that is smaller than the
outer diameter of the hollow cylindrical first portion 15.
[0041] As can be seen in particular in FIG. 7, the second portion
16 is asymmetric with respect to a plane including a cylinder axis
Z. Here, a lower edge 16c is inclined with respect to the hollow
cylindrical first portion 15 at an angle .alpha.. By means of this,
the bone anchoring element 1 can pivot at a greater angle to one
side or direction relative to the cylinder axis 2, as compared to
other sides or directions, when the bone anchoring element 1 is
seated in the seat 16a. It shall be noted that the seat member 5
can be sized such that a pivot angle of the bone anchoring element
1 with respect to one side can be as little as approximately
10.degree., while being as much as approximately 40.degree. to
50.degree. towards an opposite side. At the same time, the size of
the pivot angle is limited to the extent that the head 3 still has
adequate support in the seat member 5. The second portion 16 is not
limited to the design shown. For example, the asymmetry can be
formed by a cut-out in a hollow spherical-shaped portion, allowing
the shank to pivot only through the cut-out. The inner surface 16a
is shown as being a spherically-shaped surface. However, the inner
surface can have other shapes, such as, for example, any tapering
shape, which is sized so as to prevent the head 3 from falling
out.
[0042] The seat member 5 may also have a plurality of coaxial
recesses 18 on the inner wall of the first portion 15, which open
to the free end of the first portion 15 and end at a distance from
the lower end of the first portion 15. The recesses 18 are provided
to create a form locking engagement with corresponding projections
on the first pressure element 6. The number and shape of the
recesses 18 is not limited to the number and shape of the recesses
shown in the figures. For example, only one recess is necessary for
a form lock connection between the first pressure element 6 and the
seat member 5.
[0043] As can be seen in particular in FIGS. 3 and 4, the scat
member 5 abuts on or against the annular edge 13 of the receiving
part 4, when the seat member 5 is inserted into the receiving part
4 and moved downward along or through the bore 9. At least a
portion of the second portion 16 of the seat member 5 extends out
of the lower opening 14 of the receiving part 4. The seat member 5
is rotatable within the receiving part 4, so that the inclined edge
16c can assume any position relative to the U-shaped recess 10. As
a consequence, the position with the enlarged pivot angle for the
anchoring element 1 can assume any orientation with respect to the
U-shaped recess 10, and therefore also with respect to the rod axis
L.
[0044] The first pressure member 6 will now be explained,
specifically with reference to FIGS. 8 to 11. The first pressure
member 6 has a substantially hollow cylindrical portion 19, an
outer diameter of which is only slightly smaller than the inner
diameter of the first hollow cylindrical portion 15 of the seat
member 5, so that, as can be seen in FIGS. 3 and 4, the first
pressure member 6 can be inserted into the first portion 15 of the
seat member 5 and is axially movable with respect to the seat
member 5. On a side configured to face the head 3, the first
pressure member 6 has a recess 20, which in this embodiment is a
spherically-shaped recess with an inner diameter adapted to the
diameter of the head 3, so that the first pressure member 6 can
exert pressure onto the head 3. When the first pressure member 6 is
inserted into receiving part 4, the first pressure member 6 rests
on the head 3. The first pressure member 6 has an axial length such
that it projects above the seat member 5 in this position, as can
be seen in FIGS. 3 and 4. At an outer surface of the cylindrical
portion 19, a plurality of coaxially extending projections 21 are
provided to engage the recesses 18 of the seat member 5, to form a
form locking connection between the first pressure member 6 and the
seat member 5. The recesses 18 at the seat member 5 also form
guides for axial movement of the first pressure member 6. In other
embodiments, instead of the plurality of recesses and projections
at the inner surface of the seat member and the outer surface of
the first pressure member, respectively, any other connection
between the seat member and the first pressure member which allows
the transmission of rotational forces from the first pressure
member to the seat member can be employed. The projections 21 end
at a distance from a top end of the first pressure member 6 and can
have a chamfer 21a to facilitate engagement with corresponding
recesses 18 of the seat member 5.
[0045] On an end opposite to the recess 20, the first pressure
member 6 includes an engagement structure 22 for engagement with a
driver or tool. In the embodiment shown, the engagement structure
22 is a hexagonal recess.
[0046] The second pressure member 7 will be explained with
reference to FIGS. 12 to 14. The second pressure member 7 is
substantially cylindrical, and has on a side configured to be
opposite to the head 3 a cylindrically-shaped recess 23, which is
sized so as to guide the rod 100 therein. By means of the recess 23
two legs 24a, 24b are formed. On a side opposite to the recess 23,
the second pressure member 7 has a coaxial recess 25, which is
sized such that the second pressure member 7 can rest on the
cylindrical portion 19 of the first pressure member 6. The second
pressure member 7 also has a shallow coaxial bore 26 to allow
access to the first pressure member 6 with a driver or tool. On an
outer sidewall of the legs 24a, 24b, two coaxial recesses 27a, 27b
are formed, which are open to a top side and closed to a bottom
side of the second pressure member 7, by means of which the second
pressure member 7 can be prevented from rotating and/or from
escaping through the top end 4a of the receiving part 4, for
example, by means of pins 28a, 28b provided at the receiving part 4
as shown in FIG. 3.
[0047] When the second pressure member 7 is inserted into receiving
part 4, the second pressure member 7 abuts on or against the first
pressure member 6 in such a way that there is a gap 29 between the
seat member 5 and the second pressure member 7, so that the second
pressure member 7 does not directly press onto the seat member
5.
[0048] As shown in FIGS. 15 and 16, the form lock connection
between the first pressure member 6 and the seat member 5 allows
transmission of a rotational force exerted by a driver or tool,
which engages the first pressure member 6 at the recess 22, to the
seat member 5, so that the seat member 5 rotates with the first
pressure member 6. Since the form lock connection between the first
pressure member 6 and the seat member 5 is such that the first
pressure member 6 can slide in an axial direction with respect to
the seat member 5, the second pressure member 7 can exert pressure
onto the first pressure member 6 to press the head 3 against the
seat member 5.
[0049] The bone anchoring device, as a whole or in part, is made of
a bio-compatible material, for example, a bio-compatible metal,
such as titanium or stainless steel, bio-compatible alloys such as
nitinol or others, or bio-compatible plastic materials, such as for
example, medical grade polyetheretherketone (PEEK). Parts of the
bone anchoring device can be made of the same material or can be
made of different materials.
[0050] The steps of use of the bone anchoring device are shown in
FIGS. 17a-17c. The bone anchoring device may be pre-assembled in
such a way that the seat member 5, the bone anchoring element 1,
the first pressure member 6 and the second pressure member 7 are
inserted into the receiving part 4, and secured against falling
out, as well as against rotation of the second pressure member 7,
for example, by means of pins 28a, 28b. In this condition, the
cylindrically-shaped recess 23 of the second pressure member 7 is
aligned with the U-shaped recess 12 of the receiving part 4. The
seat member 5 abuts on or against the annular edge 13 of the
receiving part 4. In the pre-assembled state, the head 3 can freely
pivot within the seat member 5. In a next step, the bone anchoring
element 1 is screwed or otherwise inserted into a bone or a
vertebra. Usually a plurality of bone anchoring elements I are used
and connected to the rod 100. Before insertion of the rod 100, the
receiving parts 4 are aligned through pivoting the receiving parts
4 relative to their corresponding heads 3. To adjust the position
of the seat member 5 in view of the desired direction with the
enlarged pivot angle, the first pressure member 6 is rotated with a
driver or tool. Since the seat member 5 is positively connected to
the first pressure member 6, the seat member 5 rotates with the
first pressure member 6. Then, as shown in FIG. 17b, the rod 100 is
inserted. Next, as shown in FIG. 17c the fixation screw 8 is
screwed in between the legs 11a, 11b of the receiving part 4 and
tightened so that the rod 100 presses onto the second pressure
member 7, which itself presses onto the first pressure member 6,
thereby locking the head 3 relative to the seat member 5.
Simultaneously, the seat member 5 is pressed against the annular
edge 13, and is thereby also fixed in its rotational position.
[0051] Modifications of the embodiments are conceivable. For
example, it is possible to omit the second pressure member, and to
press directly with the rod onto the first pressure member. In a
further modification, the second pressure member has legs which
extend above an inserted rod, while the fixation element may be a
two-part fixation element, with an outer screw acting on the second
pressure element and an inner screw acting on the rod. In a further
modification, various different kinds of bone anchors can be used
for the bone anchoring element, such as bone nails, other types of
bone screws, canulated screws, etc. In addition, the head and the
shaft of the bone anchoring element may be separate parts that are
connectable to each other.
[0052] FIGS. 18a to 20 show an example of a tool and a method for
adjusting a rotational position of the seat member 5. A support
block 30 is provided which has a longitudinal bore 31 extending
from a top surface 30a into the support block 30. In the top
surface 30a, a recess 32 is formed that extends into the support
block 30, the recess 32 having an inner surface 32a corresponding
to the outer surface 16b of the second portion 16 of the seat
member 5. Hence, the recess 32 is asymmetrical and adapted to the
shape of the lower portion 16 of the seat member 5. As shown in
FIGS. 19 and 20, when the pre-assembled bone anchoring device is
inserted with the threaded shaft 2 into the hole 31, the second
portion 16 of the seat member 5 rests in the recess 32 and is
prevented from rotating therein due to the form lock or matching
connection.
[0053] Once the bone anchoring device is fully inserted in the bore
31, the bone anchoring element 1 and/or the receiving part 4
including the second pressure member 7 may be rotatable with
respect to the seat member 5 and the first pressure member 6.
Hence, the receiving part 4 can be rotated with respect to the seat
member 5 and the first pressure member 6, so that the enlarged
pivot angle of the seat member 5 has a desired orientation. Two
examples with different orientations are shown in FIGS. 18b and
18c.
[0054] Adjustments using the support block 30 can be made before an
actual surgery or procedure takes place, and can serve for
adjusting or setting a pre-orientation of the seat member 5. For
holding a preselected orientation of the seat member 5, an
insertion tool for inserting the bone anchoring element 1 into the
bone can be used, which is shown in FIGS. 21 and 22. Insertion tool
50 has a first portion 51 with a handle 52 at one end, a tip 53 at
the other end, and adjacent to the tip 53, an externally threaded
portion 54 for cooperating with the internal thread 12 on the legs
11a, 11b of the receiving part 4. The tool further has a second
portion 55 with two side flanges 55a, 55b for engaging the U-shaped
recess 10 of the receiving part 4. The first portion Si is
rotatable with respect to the second portion 55. When the tool 50
engages the bone anchoring device, the second portion 55 holds the
receiving part 4 through engagement with the U-shaped recess, and
the tip 53 presses onto the head 3 when the threaded portion 54 is
screwed in between the legs 11a, 11b. The orientation of the seat
member 5 is thereby secured by the pre-tension created by the tool
50, and the shaft 2 can then be inserted into the bone with the
insertion tool 50.
[0055] In an alternative method, the bone anchoring device can be
inserted into a bone with a tool 60, as shown in FIG. 23, which has
a simple drive portion 61 at its end, for example a torx driver. In
this case, a rotational orientation of the seat member 5 may not be
maintained during insertion into the bone. After insertion of the
shaft 2, a separate driver or tool for engagement with the recess
22 of the first pressure member 6 is used to adjust the rotational
position of the seat member 5 from the top end.
[0056] A visible mark can be provided to serve as an indicator for
the particular position of the seat member 5.
[0057] While the present invention has been described in connection
with certain exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed embodiments, but is
instead intended to cover various modifications and equivalent
arrangements included within the spirit and scope of the appended
claims, and equivalents thereof.
* * * * *